Stellar activity from observations with the KEPLER space telescope: The M dwarf GJ 1243

We used continuous observations with the KEPLER space telescope during 44.45 days to study the activity of the fully convective low-mass M dwarf GJ 1243. The star’s rotational period is 0.593 days. Our precision photometry of GJ 1243 made it possible to study its surface temperature inhomogeneities and follow their evolution. We find evidence for two active longitudes on the surface of the star, separated by 203° in longitude or 0.56 in phase. The position of spots on the surface was found to be very stable during the analyzed 74 rotation periods. Assuming that the rotational axis is inclined to the line of sight by i = 60°, the total spotted area S is, on average, 3.2% of the total visible stellar surface, and increased by 0.7% in 100 days; if i = 30°, the area is S = 5.6%. The change in S is due to an increase in the area of the smaller active region. We compare the magnetic-activity features of GJ 1243 and another fully convective star, V374 Peg.     

Restructuring of the Solar Magnetic Fields and Flare Activity Centers in Cycle 24

The development of the solar magnetic activity in cycle 24 has been analyzed. It has been shown that the significant north–south asymmetry of magnetic activity was accompanied by the asynchronous reorganization of solar magnetic fields in the northern and southern hemispheres. The formation of unipolar magnetic regions after the decay of activity centers has been studied. The meridional transport of unipolar magnetic regions leading to changes in the zonal structure of the solar magnetic field has been shown. Long-lived centers of flare activity have been found to exist during the periods of magnetic field restructuring. The spatiotemporal analysis of the flare ensemble making it possible to diagnose non-stationary processes in the solar atmosphere has been shown.     

Active Regions on the Sun with Increased Flare Activity in Cycle 24

Astronomy Reports - The active regions (ARs) on the Sun, which are distinguished by high values of the flare index and simultaneously developed outside activity complexes (ACs), have been analyzed....     

Unusual Photometric Activity of the Weak-line T Tauti Star V715 Per

The results of many-year photometric observations of the weak-line T Tauri star V715 Per in the optical (V RI) and infrared (JHK) photometric bands are presented. The period of the star’s lowamplitude brightness variations in the V RI bands detected earlier, 5.23d, is confirmed. This period persists during the entire 14-year time interval of the observations, but its amplitude varies with time. The same period was found in the variations of JHK infrared fluxes, with the brightness variations in the two ranges being almost synchronous. The most probable origin of these variations is periodic eclipses of the star by its own disk, perturbed by its interaction with the magnetosphere (AA Tau-type variations). In addition to the periodic brightness variations, the star also displayed sporadic Algol-like minima characteristic of UX Ori stars during several years (2005–2011). The amplitude of these variations increasedmonotonically, reaching approximately 1^m in the V band by the end of 2010, after which the deep fadings ended. During this entire time interval, the amplitude of the periodic variations was observed to decrease. After 2011, the periodic component began to become stronger again. These changes of the photometric activity of V715 Per can be explained by an increasing rate of gas accretion onto the star, decreasing the radius of warped regions of the disk and leading to accompanying Algol-like fadings. This model assumes a low inclination of the circumstellar disk in V715 Per to the line of sight.     

Destruction of a Star during the Evolution of a Star + Supermassive Black Hole System

Astronomy Reports - Stars located closely to supermassive black holes (SMBHs) can, under certain conditions, form close binary systems with the SMBHs, in which the star may fill the Roche lobe and...     

Analysis of the Eruptive Event after the Solar Flare of June 7, 2011

Astronomy Reports - We present the results of the analysis of the observational data for the eruptive event of June 7, 2011 obtained both on spacecraft (SDO, LASCO) and using ground-based solar...     

A Star of Vacuum-like Matter

A model of a star consisting of vacuum-like matter is constructed in the framework of general relativity. Its stability and other physical properties are analyzed. This stellar model is compared with cosmological models consisting of the same vacuum-likematter with a pressure equal to the energy density but with the opposite sign.

     

Star formation and the kinematics of gas in the disk of NGC 628

The radial profile of the star-formation rate (SFR) in the galaxy NGC 628 is shown to be modulated by a spiral-density wave. The radial profile of the velocity of gas inflow into the spiral arm is similar to the radial distribution of the surface density of the SFR. The position of the corotation resonance is determined along with other parameters of the spiral-density wave via a Fourier analysis of the azimuthal distribution of the observed radial velocities in annular zones of the disk of NGC 628. The radial profile of the surface density of the SFR is determined using the empirical SFR—linear size relation for star-formation complexes (giant HII regions) and measurements of the coordinates, Hα fluxes, and the sizes of HII regions in NGC 628.     

An Unusually Powerful Water-Maser Flare in the Galactic Source W49N

The most powerful flare ever registered in the Galactic water-maser source W49N has been detected in long-term monitoring data in the 6₁₆–5₂₃ transition with line frequency f = 22.235 GHz carried out on the 22-m Simeiz, 32-m Toruń, 100-m Effelsberg, and 32-m Medicina radio telescopes, beginning in September 2017 and continuing in 2018. Some stages of the flare were monitored daily. Detailed variations of the source spectral flux density with time have been obtained. At the flare maximum, the flux exceeded P ≈ 8 × 10⁴ Jy, and this was record highest flux registered over the entire history of observations of this source. Important conclusions related to details of the mechanism for the H₂O line emission have been drawn. An exponential increase in the flare flux density was detected during both the rise and decline of the flare. The data obtained indicate that the maser is unsaturated, and remained in this state up to the maximum observed flux densities. Additional support for the idea that the maser is unsaturated is the shape of the dependence of the line width on the flux. The characteristics of the variations of the spectral flux density are probably associated with a sharp increase in the density of the medium and the photon flux that led to an increase in the temperature from an initial level of 10–40 K to hundreds of Kelvins. Interferometric maps of the object during the increase in the spectral flux density of the flare have been obtained. A possible mechanism for the primary energy release in W49N is considered.

     

A Giant Water Maser Flare in the Galactic Source IRAS 18316-0602

Astronomy Reports - The results of long-term monitoring of the Galactic maser source IRAS 18316–0602 (G25.65+1.05) in the water-vapor line at frequency f = 22.235 GHz (616–523...     

合成扩散星光刚玉的物理性质及成因探讨

通过常规的宝石学测试方法、电子探针分析及紫外-可见光谱分析等测试, 详细研究了3块待测样品的化学成分和物理性质, 并将其与天然刚玉及合成星光刚玉进行了对比研究.3块待测样品的颜色分别为橙红色、褐红色及紫红色, 透明度较高, 其中橙红色的为近透明, 另外2粒为半透明.强光下发现样品的表面有一层云雾状的物质.星光浮于表面, 且较为发散、弯曲.星光相交处可见宝光.显微镜下观察发现, 3块样品的表面均有较多的凹坑, 其中2块近表面可见隐约的丝状包裹体, 但定向性较差; 1块似有熔融的特征.这些特征表明, 这3块样品中包裹体可能是经过高温处理而成, 非合成退火所致.3块样品均可见到较明显的细密的弯曲生长纹, 表明其为焰熔法合成产物.电子探针分析结果显示, 3块样品的致色元素均为铬, 为红宝石; 丝状体为钛酸铝.紫外-可见光谱测试结果表明, 其吸收光谱为铬吸收谱.综合分析所有的特征, 认为这3块样品为焰熔法合成红宝石, 星光的产生是在合成红宝石生成加工后, 通过扩散作用所形成的丝状钛酸铝对光的反射所致.      

The Influence of a Stellar Flare on the Dynamical State of the Atmosphere of the Exoplanet HD 209458b

A one-dimensional aeronomic model of the upper atmosphere of a giant planet is used to study the reaction of the atmosphere of the hot Jupiter HD 209458b to additional heating by a stellar flare. It is shown that the absorption of additional energy from the stellar flare in the extreme ultraviolet leads to local heating of the atmosphere, accompanied by the formation of two shocks propagating in the atmosphere. Possible observational manifestations of these shocks and the feasibility of their detection are discussed.     

Neutron Star Mergers and Gamma-Ray Bursts: Stripping Model

Astronomy Reports - This paper provides an overview of the current state of the stripping model for short gamma-ray bursts. After the historical joint detection of the gravitational wave event...     

Unusual Eclipse of the UX Ori Type Star V719 Per

Astronomy Reports - The results of new photometric ( $$VRI$$ ) observations of the young star V719 Per from the IC 348 cluster are presented. Up until 2014, this star demonstrated brightness...     

On the Status of the Star Schulte 12 in the Association Cyg OB2

Astronomy Reports - High-resolution spectra of the LBV candidate Schulte 12 in the Cyg OB2 association were obtained at the 6-m BTA telescope with the NES echelle spectrograph on the arbitrary...     

Modeling of Spectroscopic and Interferometric Observations of the Herbig Star VV Ser with Hybrid Models

Modeling of hydrogen emission lines is a powerful tool to study physical processes in the nearest vicinity of young stars because spectral lines carry information on the kinematics and physical conditions of the gas. One of the lines that probe emitting regions closest to the star is the Br$$\gamma $$ line. We consider different types of hybrid models to reproduce both interferometric VLTI-AMBER observations and LBT-LUCIFER spectroscopic observations of the single-peak profile of the Br$$\gamma $$ line of the Herbig AeBe star (HAEBE) VV Ser, a member of the UX Ori type subclass. We computed models of a magneto-centrifugal disk wind, a magnetospheric accretion region (magnetosphere), Cranmer’s polar wind, and scattered light from circumstellar polar dust. Furthermore, we calculated hybrid two-component models consisting of a disk wind and one of the aforementioned models. We computed visibilities and line profiles for all types of models and compared them with the available interferometric observations to constrain model parameters. We conclude that for the inclinations reported for this star (60°–70°), the disk wind alone cannot explain the Br$$\gamma $$ line profile although it may be a dominant contributor to the hydrogen line radiation. However, magneto-centrifugal disk wind in combination with aforementioned emitting regions (magnetosphere, polar wind, or scattered light from polar dust) may be able to reproduce the observations.     

Results of Many-year Photometry of the Herbig Ae Star AB Aur in the Near Infrared

Astronomy Reports - The results of many-year infrared observations of the Herbig AeBe star AB Aur at 1-5 μm (JHKLM bands) are presented. The duration of the photometric series, together with...     

Observational Manifestations of the Precessional Wave in the Accretion Disk of a Cataclysmic Variable Star

Effects due to the interaction of the steam from the inner Lagrangian point with the accretion disk in a cataclysmic variable star are considered. The results of three-dimensional gas-dynamical numerical simulations confirm that the disk thickness in the vicinity of the interaction with the stream is minimum when the component-mass ratio is 0.6. As a consequence, some of the matter from the stream does not collide with the outer edge of the accretion disk, and continues its motion unperturbed toward the accretor. This part of the stream subsequent interacts (collides) with a thickening of the accretion disk due to the presence of a precessional wave in the disk, leading to the appearance of an additional zone of heating at the disk surface. This additional zone of enhanced luminosity (hot spot) is a direct observational manifestation of the precessional wave in the accretion disk.     

Sedimentologic and stratigraphic constraints on emplacement of the Star Kimberlite, east–central Saskatchewan

Diamond-bearing kimberlites in the Fort à la Corne region, east–central Saskatchewan, consist primarily of extra-crater pyroclastic deposits which are interstratified with Lower Cretaceous (Albian and Cenomanian) marine, marginal marine and continental sediments. Approximately 70 individual kimberlite occurrences have been documented. The Star Kimberlite, occurring at the southeastern end of the main Fort à la Corne trend, has been identified as being of economic interest, and is characterized by an excellent drill core database. Integration of multi-disciplinary data-sets has helped to refine and resolve models for emplacement of the Star Kimberlite. Detailed core logging has provided the foundation for sedimentological and volcanological studies and for construction of a regionally consistent stratigraphic and architectural framework for the kimberlite complex. Micropaleontologic and biostratigraphic analysis of selected sedimentary rocks, and U–Pb perovskite geochronology on kimberlite samples have been integrated to define periods of kimberlite emplacement. Radiometric age determination and micropaleontologic evidence support the hypothesis that multiple kimberlite eruptive phases occurred at Star. The oldest kimberlite in the Star body erupted during deposition of the predominantly continental strata of the lower Mannville Group (Cantuar Formation). Kimberlites within the Cantuar Formation include terrestrial airfall deposits as well as fluvially transported kimberlitic sandstone and conglomerate. Successive eruptive events occurred contemporaneous with deposition of the marginal marine upper Mannville Group (Pense Formation). Kimberlites within the Pense Formation consist primarily of terrestrial airfall deposits. Fine- to medium-grained cross-stratified kimberlitic (olivine-dominated) sandstone in this interval reflects reworking of airfall deposits during a regional marine transgression. The location of the source feeder vents of the Cantuar and Pense kimberlite deposits has not been identified. The youngest and volumetrically most significant eruptive events associated with the Star Kimberlite occur within the predominantly marine Lower Colorado Group (Joli Fou and Viking Formations). Kimberlite beds, which occur at several horizons within these units, consist of subaerial and marine fall deposits, the latter commonly exhibiting evidence of wave-reworking. Black shale-encased resedimented kimberlite beds, likely deposited as subaqueous debris flows and turbidites, are particularly common in the Lower Colorado Group. During its multi-eruptive history, the Star Kimberlite body is interpreted to have evolved from a feeder vent and overlying positive-relief tephra ring, into a tephra cone. Initial early Joli Fou volcanism resulted in formation of a feeder vent (200 m diameter) and tephra ring. Subsequent eruptions, dominated by subaerial deposits, partly infilled the crater and constructed a tephra cone. A late Joli Fou eruption formed a small (70 m diameter) feeder pipe slightly offset to the NW of the early Joli Fou feeder vent. Deposits from this event further infilled the crater, and were deposited on top of early Joli Fou kimberlite (proximal to the vent) and sediments of the Joli Fou Formation (distal to the vent). The shape of the tephra cone was modified during multiple marine transgression and regression cycles coeval with deposition of the Lower Colorado Group, resulting in wave-reworked kimberlite sand along the fringes of the cone and kimberlitic event deposits (tempestites, turbidites, debris flows) in more distal settings.     

A Survey of High Mass Star Forming Regions in the Lines of Deuterated Molecules

Astronomy Reports - A survey of massive star forming regions in the lines of the lowest transitions of deuterated molecules DCN, DNC, DCO+, N2D+ in the 4 mm wavelength range was performed using the...